Control pulse system for knitting machines

ABSTRACT

In a knitting machine with electromagnetic selection of the needles, excitation of the electromagnets is controlled by pulses at the revolutions per minute (speed) of the machine. The time constant of the electromagnets at high machine speeds is compensated by shifting the phase of the pulses in accordance with the machine speed. Phase shift at low speeds is unnecessary.

United States ate [1 1 Cuche ll 3,745,791 July 17,1973

[ 1 CONTROL PULSE SYSTEM FOR KNITTING MACHINES [75] Inventor: Claude C. A. Cuche, Neuchatel,

Switzerland [73] Assignee: Edouard Dubied et Cie S .A.,

Neuchatel, Switzerland 22 Filed: Dec. 31, 1910 211 App1.No.:103,239

30 Foreign Application Priority mm Jan. 28, 1970 Switzerland ll94/70 [52] US. Cl. 66/50 R, 66/56 [51] Int. Cl D041) 15/78 58 Field arse-ruin; 66/50 R, 50 A, 50 B, 66/25, 154 A, 56

[56 References Cited UNITED STATES PATENTS 3,709,002 1/1973 Brandt et a1, 66/50 R X Macqueen 66/154 A X 3,327,499 6/1967 Schmidt et a1 66/154 A X 3,406,539 10/1968 Wiesinger et al. 66/56 3,427,830 2/1969 Uhlir 3,446,037 5/1969 Sutton 3,470,714 10/1969 Corbaz 66/50 R FOREIGN PATENTS OR APPLICATIONS 136,844 0/1961 U.S.S.R 66/154 A Primary Examiner-Wm. Carter Reynolds Altorney-Kenyon & Kenyon Reilly Carr & Chapin [57] ABSTRACT In a knitting machine withe lectromagentic selection of the needles. excitation cf the electromagnets is controlled by pulses at the revolutions per minute (speed) of the machine. The time constant of the electromagnets at high machine speeds is compensated by shifting the phase of the pulses in accordance with the machine 1 speed. Phase shift at low speeds is unnecessary.

2 Claims, 4 Drawing Figures BACKGROUND OF THE INVENTION The electromechanical needle selection in a knitting machine is efiected by electromagnets, which select push rods or other ferromagnetic parts, which in turn act on the needles. The excitation of the electromagnets is effected by electrical impulses which are read from a program by means of a reading device (termed another source). The magnets have their own particular time constant and are affixed to a machine with which they must act synchronously. The speed of the machine varies between zero and a maximum value. This fixed time constant must be compensated by causing the impulses to act on the electromagnets as early as is necessary to obtain the mechanical effect at the correct moment. For this purpose a phase shifter has previously been proposed (Swiss Patent 410.123) (US. Pat. No. 3,470,714 Corbaz) which generates three pulse sequences displaced in respect of one another and assigns a given pulse sequence to a range of machine speeds. This proposal offers a perhaps sufficient, but in no way optimum solution, to the problem, since in each range the control orders are released at the optimum time only for a single speed of the whole range of speeds.

SUMMARY OF THE INVENTION An object of the present invention is to provide a phase shifter which releases the control orders for all possible machine speeds, with the exception of the minimum speeds, at the quasi-optimum point of time.

For low speeds a compensation is unnecessary, as the time constant of the electromagnets is substantially less than the travel time of the push rods before them. Because of this, the phase shifter can be substantially simplified.

The phase shifter in accordance with the invention is characterized in that a logical system adapting pulses coming from the pulse generator is connected to two circuits, one of which, for the low speeds, connects the adaptive logical system direct to a change-over and shaping logical system, while the other, for the higher speeds, connects the adaptive logical system via a delay circuit, a first integrator and a first Schmitt trigger to the change-over and shaping logical system, and in that the changing-over from one circuit to the other, which is efiected by the change-over and shaping logical sys- I tem, is controlled by a tachometer circuit containing a second Schmitt trigger, which is controlled by a second integrator.

THE DRAWINGS FIG. 1 is a block diagram of the phase shifter, and

FIG. 2 shows the shape of the pulses at different terminals of the phase shifter, the abscissae representing the geometrical position of the needles on the machine.

FIGS. 3 and 4 show ways of implementing the portions 3 and 5 respectively of FIG. 1.

PREFERRED EMBODIMENT Input terminals 1, 2 of an adaptive logical system 3 are electrically connected to a pulse generator (which may be of any known type and is therefore not described in more detail) fixed on the knitting machine, or frame. The said pulse generator produces two cyclic pulse sequences U U,, which are electrically displaced in respect of one another by the first sequence being fed to the terminal I and the second sequence to the terminal 2. The adaptive logical system 3 changes the cyclic relationship of the pulses. The form, which can be'determined at the terminal 4, is represented by the pulse sequence H As one skilled in the art-will readily perceive, the adaptive logical system 3 may be constructed as shown in FIG. 3. In FIG. 3, conventional transistor circuits 22 and 23 impose the pulse sequences U1 and U2 from inputs l and 2 on NAND gates 24 and 25 as shown, NAND gate 24 being connected as inverter. In a conventional manner, npn-transistors 22,23 amplify pulse sequences U1 and U2, respectively, and invert their logic. N AND gate 24 inverts again the logic of inverted U2 for input to NAND gate 25 so that NAND gate 25 having the pulse sequence U]. with inverted logic and the pulse sequence U2 at its inputs may produce H4 as an output.

The adaptive logical system 3 is connected via two circuits with the output side of the phase shifter. The

said output side is a change-over and shaping logical system 5, herein referred to as an output logical system 5, for short.

The first circuit, for low speeds, is a direct connection arrangement, effected by a connecting line 6. In the present embodiment by low speeds are meant speeds from zero to three revolutions per minute of the needle cylinder, and by higher speeds are meant speeds of more than three revolutions per minute.

In the second circuit, for the higher speeds, the adaptive logical system 3 is connected to a delay circuit 7 which delays the descending flanks of the pulses of the pulse sequence P terminal 8, in relation to the descending flanks of the pulses M by a time interval At (represented by a length Ax).

It is advantageous to provide an adjustable delay circuit 7, in order to obtain a single embodiment for different types of knitting machines and various needle distributions.

The delay circuit 7 is connected to an integrator 9, which works with constant current strength. The said currents generate a cut-off saw-tooth voltage which is represented by the sequence D terminal 10. During the time (represented by the length d) for which a pulse of the sequence D lasts, the voltage decreases at a constant rate, and at the end of this pulse it increases at a different constant rate. It is known to obtain rates (graph gradients) of this kind by charging/discharging a capacitor at constant currents. The constant voltage represented by the horizontal line h between two sawteeth, is used for controlling a Schmitt trigger II. The pulse sequence occurring at the output side (terminal 12) of the trigger II is represented by H The said output is connected to the output logical system 5, which latter, controlled by the flanks f, generates calibrated pulses. These are represented by the pulse sequence H terminal 13.

The output logical system 5 changes over from one circuit to the other. In order to do this it is controlled by a tachometer circuit. The latter utilizes the pulses of the sequence H. to determine the machine speed and to generate a corresponding shift signal. This signal is shown in graph T,-, terminal 17. The moment of shifting is shown by the flank t. The tachometer circuit comprises an integrator 14 with constant current, which generates a variable voltage represented by the graph D terminal 15. If this voltage does not reach a predetennined limit value, that is when the machine speed is greater than the mentioned value of three revolutions per minute, then a Schmitt trigger 16 changes its condition. The said trigger is connected to an integrator 14 and its condition is represented by the graph T terminal 17.

As one skilled in the art will readily perceive, the output logical system 5 may be constructed as shown in FIG. 4. The output logical system 5 of FIG. 4 is formed by NAND gates 26, 27 and 28, and pulse shaping circuit 35.

At speeds below 3RPM, NAND gate 26 has inverted H4 as an output. At speeds above 3RPM, the output of NAND gate 26 is not inverted H4 but a constant value. Conversely, at speeds below 3RPM, NAND gate 28 has a constant output, while above BRPM, NAND gate 28 has inverted H12 as an output. As is obvious to one skilled in the art, the combined output of NAND gates 26 and 28 is, therefore, inverted H4 at speeds below 3RPM and inverted H12 at speeds above SRPM. The foregoing is in accordance with the conventional NAND gate logic and takes into account the fact that NAND gate 27 inverts T17.

Pulse shaping circuit 35 is well within the skill in the art and converts the H4 and H12 outputs of NAND gates 26 and 28 into H13.

The NAND circuits of FIGS. 3 and 4 are preferred because of their well known reliability and inexpensiveness (compared to older switching techniques which would perform the functions of elements 3 and 5 of FIG. 1.

It is obvious to one skilled in the art that Schmitt trigger 16 may be operated from one to the other of its two states indicated by T17 simply by monitoring the peak values of D15. It is very old in the art to sample a signal for its peak value by means of a sampling pulse occurring at the time of each peak value. It is evident from FIG. 3 that the peak values of D15 occur at the time of the trailing edges of H4 and it lies within the skill of the art, indeed it is obvious, to derive the required sampling pulses from H4. Since the peak values of D15 before BRPM are distinctly different from those above 3RPM, as indicated by the horizontal lines at peak levels, these values may be used for operating the Schmitt trigger 16 from one or the other of its two states indicated by T17.

At low speeds the output logical system 5 utilizes the flanks g of the pulse sequence H, for releasing the calibrated pulses of the sequence H The calibrated pulses coming from the phase shifter are amplified in an amplifier 18, and by means of a storage device 19, they control the further conductance of the programme pulses, the control orders which originate from another source 20, to the electromagnets of the knitting machine 21. The source 20 may be a programme reader, a data processing unit, or the like.

The calibrated pulses can further control the step-bystep conveying of the programme carrier and/or the moment for reading off the same and/or the moment for reading information from a store.

I claim:

1. A generator of pulses with phase displacement which initiate in a knitting machine with electromechanical needle selection the carrying out of control orders originating from another sourse, the amount of the phase displacement being a function of the speed of the knitting machine, which machine drives a pulse generator which is electrically connected with the generator of pulses with phase displacement, characterized in that an adaptive logical system including gates combining and adapting the pulses coming from the pulse generator, is connected to two circuits, one of which, for low speeds, connects the adaptive logical system directly with a change-over and shaping logical system including gates, and the other of which, for the higher speeds, connects the adaptive logical system via a delay circuit, a first integrator, and a first trigger with the change-over and shaping logical system and so that the changing-over from one circuit to another, which is effected by the change-over and shaping logical system, is controlled by a tachometer circuit comprising a second trigger, which is controlled by a second integrator.

2. A generator as claimed in claim 1, wherein the delay circuit can be regulated. 

1. A generator of pulses with phase displacement which initiate in a knitting machine with electromechanical needle selection the carrying out of control orders originating from another sourse, the amount of the phase displacement being a function of the speed of the knitting machine, which machine drives a pulse generator which is electrically connected with the generator of pulses with phase displacement, characterized in that an adaptive logical system including gates combining and adapting the pulses coming from the pulse generator, is connected to two circuits, one of which, for low speeds, connects the adaptive logical system directly with a change-over and shaping logical system including gates, and the other of which, for the higher speeds, connects the adaptive logical system via a delay circuit, a first integrator, and a first trigger with the change-over and shaping logical system and so that the changing-over from one circuit to another, which is effected by the change-over and shaping logical system, is controlled by a tachometer circuit comprising a second trigger, which is controlled by a second integrator.
 2. A generator as claimed in claim 1, wherein the delay circuit can be regulated. 